During rolling of spur gears in gearing arrangements, which are lubricated by a lubricant having a high viscosity, or in gearings with oils having a lower viscosity or high rotational speed, high power losses may occur caused by the squeezing of oil out from between the teeth, in particular when the mating spur gears are so wide that most of the oil must exit in direction of the tooth height and only a small part can escape at the axially facing sides of the gear.
Spur gear systems having herringbone teeth are already known and which have in the center of the tooth width a peripheral groove so that the gear cutting tool has sufficient space to work the teeth. In these spur gears, the oil does not only escape toward the outer axially facing ends, but also toward the peripheral grooves. The power loss is thereby less. These peripheral grooves have so far only been used in herringbone spur gears for technical manufacturing reasons, while the reduction of the power loss has been up to now a side effect which has been virtually unconsidered. Herringbone gears are relatively expensive and the peripheral grooves effect possibly an undesired interrupted cut of the gear tool.
Therefore the basic purpose of the invention is to find a structure which will reduce the power loss through trapped oil, in which exists a cheaper type of toothing, and in which the interrupted cut is avoided as much as possible.